Expansion turbine

ABSTRACT

An expansion turbine, exhibiting at least one turbine rotor that is mounted on an axial bearing, wherein an axial disk ( 2   l ) of the axial bearing is configured in the shape of an axial bearing spindle. The axial disk ( 2   l ) is preferably positioned substantially in the middle of the overall length of the turbine shaft ( 1 ).

The invention relates to an expansion turbine that has at least oneturbine rotor that is mounted on an axial bearing.

Expansion turbines have been used for a long time for cooling in thecase of industrial gases, such as, for example, hydrogen, helium andnitrogen. In this case, heat is removed from the process gas to bedepressurized via substantially isentropic gas depressurization and theconversion of the force of flow in a rotational movement of the turbinerotor to the process gas. Thus, the process gas to be depressurized iscooled in this process in the turbine stage.

Various designs exist for the bearing arrangement of expansion turbines.Dynamic gas-bearing expansion turbines have gas bearings that do notrequire an external supply of gas bearings to operate. Only for startingup and shutting down is a temporary supply with bearing gas necessary.In the case of dynamic gas-bearing expansion turbines, radial bearingsand an axial bearing are used for the bearing arrangement of the turbineshaft. The central functional element of the axial bearing arrangementhere is the axial disk that takes up the axial thrust on the turbineshaft in the direction of the turbine and in the opposite direction.

BRIEF DESCRIPTIONS OF THE DRAWINGS

The generic expansion turbines or their axial bearing arrangement can beexplained in more detail below based on the embodiment that is shown inFIGS. 1 a and 1 b. In this connection,

FIGS. 1 a and 1 b show schematized lateral sectional views through theembodiment.

An upper axial bearing 3 and a lower axial bearing 4 are shown. Theaxial bearings 3 and 4 are used to take up the axial disk 2 that isconnected to the turbine shaft 1. The axial disk 2 together with theaxial bearing 3 on the one hand and the axial bearing 4 on the otherhand in each case forms two pairs of bearing effective surfaces. Thesepairs of bearing effective surfaces have the object of taking up theaxial thrust in both possible directions along the axis of rotation ofthe turbine shaft 1.

The actual zone of the bearing arrangement is in the bearing effectivesurfaces near the shank of the turbine shaft 1 in the inner area of theaxial disk 2. The outer area of the bearing effective surfaces primarilyconveys gas from outside to inside in the bearing zone. The zone ofmaximum load capacity is marked with a circle 5 in FIG. 1 a.

If high peripheral speeds now occur, the bearing effective surfaces ofthe axial disk 2 deform—as shown in FIG. 1 b—by a few microns inabsolute length in an elastically concave manner. This undesirable,elastically concave deformation reduces the load capacity of the axialbearing for the following reasons:

The load capacity is determined essentially by the distance between thepair of bearing effective surfaces on the rotor (axial disk 2) to thestator (axial bearing 3 or axial bearing 4). The distance between thebearing effective surfaces from the rotor to the stator is only a fewmicrons in the state of operation. In principle, it holds true that thesmaller the possible distance that is to be set between the bearingeffective surfaces, the greater the load capacity of the axial bearing.The elastically concave deformation of the bearing effective surfaces onthe rotor reduces the possible distance to be set between the bearingeffective surfaces. The elastic deformation on the outside edge of therotor (axial disk 2) increases the minimum possible distance to thestator (axial bearing 3 or axial bearing 4), since otherwise, if thebearing effective surfaces are too close together, the rotor and statorwill collide. In this case, it holds true that: the load capacitydecreases with increasing distance of the bearing effective surfacesfrom rotor and stator.

With increasing speed, a latent imbalance of the turbine rotor 1 resultsin increasing wobbling of the axial disk 2. Because of the unfavorableelastically concave deformation on the outside edge, the wobblingincreases the risk of collision and reduces the bearing effectivesurface on the axial disk 2.

Moreover, the elastically concave deformation of the axial disk 2counteracts the functioning of the axial bearing arrangement—namely ageometric unit that pumps from the outside inward, with across-sectional constriction and delayed flow, leading to pressurebuild-up.

Based on the indicated properties of the existing design, the potentialand functionality of the bearing effective surfaces for the axialbearing cannot be exhausted at higher rpms.

The object of this invention is to provide expansion turbine, exhibitingat least one turbine rotor that is mounted on an axial bearing, whichavoids the previously described drawbacks.

To achieve this object, an expansion turbine that has at least oneturbine rotor that is mounted on an axial bearing is proposed, which ischaracterized in that the axial disk of the axial bearing is designed inthe form of an axial bearing spindle.

Corresponding to another advantageous embodiment of the expansionturbine according to the invention, the axial disk is arrangedessentially in the middle of the overall length of the turbine shaft orthe turbine rotor.

The expansion turbine according to the invention as well as otherconfigurations of the same can be explained in more detail below basedon the embodiment that is shown in FIGS. 2 a and 2 b. In thisconnection, FIGS. 2 a and 2 b show schematized lateral sectional viewsthrough the embodiment.

In turn, an upper axial bearing 3 and a lower axial bearing 4 are shown.As is readily seen in FIGS. 2 a and 2 b or the axial disc has a concaveperiphery 6 formed by surfaces 7 and 8 that converge toward nadir 9.Serve to hold the axial disk 2′, which is connected to the rotor shaft1, which axial disk is designed, according to the invention, in the formof an axial bearing spindle. The zone of maximum load capacity is alsolabeled with a circle 5 in FIG. 2 a.

If high peripheral speeds now occur, the result is also an elasticand—because of the spindle shape—convex deformation of the bearingeffective surfaces of the axial disk 2′ by a few microns in absolutelength, as is shown in FIG. 2 b. This elastic convex deformation nowincreases the load capacity of the axial bearing, however, for thefollowing reasons:

The elastic convex deformation of the axial disk 2′ that occursinfluences the distance of the bearing effective surfaces that is to beset between the rotor (axial bearing spindle) and the stator (axialbearing 3 or 4) in a positive way. The minimum possible distance of thebearing effective surfaces between the rotor and the stator is reduced,and the maximum load capacity is increased.

The axial disk 2′ is preferably arranged in the middle of the overalllength of the turbine rotor. Because of the geometric shaping of theaxial disk 2′ as an axial bearing spindle, the gyroscopic effect of aspinning top counteracts possible wobbling induced by a latent imbalanceof the turbine shaft 1. The convexity of the elastic convex deformationof the bearing effective surfaces of the rotor is uncritical compared toa possible risk of collision on the outside edge of the axial disk 2′.

Moreover, the elastic convex deformation of the axial disk 2′ issupportive of the functioning of the bearing effective surfaces. Across-sectional constriction occurs from the outside edge of the axialdisk 2′ inward to the bearing effective surface near the shank 1 of theturbine rotor. Thus, the compression action of the bearing effectivesurfaces is required.

Because of the cited properties of the expansion turbine according tothe invention, the potential and functionality of the bearing effectivesurfaces for the axial bearing can now be fully exhausted at higher rpmsfor the first time.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The preceding preferred specific embodiments are,therefore, to be construed as merely illustrative, and not limitative ofthe remainder of the disclosure in any way whatsoever.

The entire disclosures of all applications, patents and publications,cited herein and of corresponding German application No. 10 2007 029881.3, filed Jun. 28, 2007 is incorporated by reference herein.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention and, withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

1. An expansion turbine, comprising at least one turbine rotor mountedon an axial bearing, wherein the bearing has an axial disk (2′)configured in the shape of an axial bearing spindle.
 2. The expansionturbine according to claim 1, wherein the axial disk (2′) is positionedin the middle of the overall length of the turbine shaft (1).
 3. Theexpansion turbine according to claim 1 wherein the axial disk (2′) has aconcave periphery.
 4. The expansion turbine according to claim 2 whereinthe axial disk (2′) has a concave periphery.